Pipe sizes

[Dirk]

I want to replumb a house i'm moving in to, it has a black plastic water main, circa 1965 and a new combi boiler installed.
My query is:

Is there any advantage in having a plastic - 22mm stop tap and having a 22mm main with 15 mm branches to outlets rather than having all the cold water in 15mm ? I was thinking it may help keep the pressure up over long runs as it would decrease pressure loss due to friction?

Cheers

 

[muggles]

Depends on the size of your incoming main, if the bore of that is no larger than 15mm pipe then it's a pointless exercise

 

[Charnwood]

If you are basing your question re using 22mm on the fact that your current pipe being about 22mm outside diameter then my answer would be no, go with 15mm.

1/2" ID black alkathene (eq bore to 15mm copper) is about 21mm OD.

 

[Nige F]

1/2" ID black alkathene (eq bore to 15mm copper) is about 21mm OD.

or 3/4" - always used 3/4 compression fittings

 

[bengasman]

If your cold mains is 22 or better all the way from the streetvalve to the bath and only branches of in 15 to other cold points, you will have a significant improvement compared to old 1/2"

 

[Charnwood]

or 3/4" - always used 3/4 compression fittings

3/4" alkathene is about 27mm OD.